1. Field of the Invention
Aspects of the present invention relate to a secondary battery, and more particularly, to a lithium polymer battery with improved stability and that includes a protective circuit cover and pouch type exterior material.
2. Description of the Related Art
Generally, a lithium polymer battery comprises an electrode assembly, pouch type exterior material receiving the electrode assembly, and a protective circuit cover placed on one side of the exterior material so as to be electrically coupled to the electrode assembly.
The electrode assembly is formed by laminating a first electrode plate, a separator and a second electrode plate, and winding them in a jelly-roll shape. The first and second electrode plates are coupled to a first electrode tap and a second electrode tap respectively, and the taps are drawn out to an outer side of the exterior material when the electrode assembly is received in the inside of the exterior material.
The exterior material is a soft pouch type, and comprises insulating layers on both sides of a metal film such as aluminum, etc. The protective circuit cover includes connecting terminals that are coupled to the electrode taps and is arranged on a front surface of the exterior material.
The exterior material includes a first region receiving the electrode assembly and a second region integrally formed on one end of the first region. The second region covers the electrode assembly when the electrode assembly is received in the inside of the first region, and both the side surfaces and a front surface of the first and second regions are heat-bonded.
Although both the side surfaces and the front surface of the first and second regions are heat-bonded, a cut region of the exterior material of the lithium polymer battery is exposed to the outside. Therefore, a portion of the metal film of the exterior material which is mostly surrounded by insulating layers, is exposed to the outside. More specifically, there is a high probability that the metal film is exposed at a leading edge region of both side surfaces of the exterior material such that it can be contacted with both end regions of the protective circuit cover formed on the front surface of the exterior material.
Conventionally, if the metal film exposed at the leading edge region of both side surfaces of the exterior material comes in contact with a pattern or a terminal of the protective circuit cover, the exterior material is corroded or, as time passes, a minute electrical short occurs between them.
Also conventionally, components on the protective circuit cover are damaged by the injection pressure of melting resin because a protective circuit element or a terminal of the protective circuit cover is installed at a position adjacent to the injection passage of the melting resin when the protective circuit cover is combined with the bare cell by a hot melt method.